NOVEL REACTIVITY OF THE DIOXYGEN MOLECULE IN THE PRESENCE OF A MANGANESE(II) COMPLEX AND REDUCING AGENTS

A manganese(II) complex with pentadentate ligand derived from 2,6-diac etylpyridine and triethylenetetramine exhibits high activity for activ ation of dioxygen in the presence of several aliphatic aldehydes, but the activities of other manganese(II) compounds with tripod-like ligan ds such as tris(2-benzimidazolylmethyl)amine or bis(2-benzimidazolylme thyl) ether are almost negligible. On the basis of these facts includi ng electrochemical data under dioxygen atmosphere, the importance of a n intermediate complex formation among aliphatic aldehyde, Mn(II) comp lex, and dioxygen is pointed out; in the intermediate, the dioxygen mo lecule is assumed to coordinate to a manganese(II) ion by hydrogen bon ding with the hydrogen atom of the chelate (-NH group), and the novel reactivity of dioxygen, i.e., the dioxygen molecule accepts an electro n from the aldehyde through formation of the intermediate to yield an organic peracid without the change of the oxidation state of the metal ion, is postulated.